Abarim Publications' online Biblical Greek Dictionary
The noun θηλη (thele) means nipple. It's not used in the New Testament, but from it derives the verb θηλαζω (thelazo), which literally means to nipple (to use nipples for what they're for). Translations into English of this verb run into a distinction between to suck (what babies do) and to give suck or to breast-feed (what mothers do), but in Greek that distinction does not exist.
In the Iliad, Homer used a particular variant of our verb, namely θαομαι (thaomai), which in turn technically derives from the verb θαω (thao), to suck. This verb θαομαι (thaomai), meaning to suck (to do the nipple-thing), is identical to the verb θαομαι (thaomai), meaning to marvel or wonder, from which come English words like theater and theory, and possibly even the familiar Greek word θεος (theos), or God.
The obvious connection between the two verbs θαομαι (thaomai) becomes clear when we realize that milk in the New Testament metaphorizes elementary instruction to intellectual babes: see for a more elaborate discussion of this our article on the noun γαλα (gala), milk.
Our verb θηλαζω (thelazo), to suckle, is used 6 times in the New Testament; see full concordance.
Obviously related to the previous, the adjective θελυς (thelus) means female, the complementary counterpart of αρσην (arsen), male.
In antiquity, femininity was associated with collectivity and masculinity with individuality — which is why nations and peoples were considered "mothers" (see our article on the Hebrew noun אם, 'em), their kings and governments (including divine government) were considered "father" (hence the noun אב, 'ab), and their citizens their "sons" (hence the noun בן, ben).
Paul's observations on males-with-males and females-with-females (Romans 1:26-27) are not about homosexuality among men and women, as certain critics volunteer, but rather on the attitudes of peoples (females) and their governments (males) toward other peoples and their governments; those great and overbearing cultural currents from which every individual derives their personal attitudes toward other individuals.
We moderns are so comfortable today that we often forget that by the time of Christ the ancient world had reached a technical and intellectual sophistication that wasn't reached again until after the Renaissance, and that the fall of Rome was in effect the fall of mankind. It took humanity more than a thousand years of dark misery to begin to arise the damage done by the Roman Empire, which resulted from the collapse of the Republic, which resulted from the Marian reforms, which followed the Punic Wars, which followed local skirmishes on Sicily, which began when Roman merchants and Phoenician merchants lost their neighborly respect for each other and began to pester and discriminate the other (see our article on the name Hannibal for more on this).
Commentators who review these texts should remember that certain activities are condemned when they arise from base lust and are condemned together with other acts of lust (Matthew 5:28). Love, on the other hand, has many manifestations but is always based on honor, respect and ultimately freedom (Luke 7:47). This in turn means that making true love (or acting out one's genuine love) happens on as blank a canvas as making a song or a painting would be, and cannot be categorized. In Christ people are freed for the sake of freedom (Galatians 5:1) and freedom has no categories; only sin does (which is how the word κατηγορος, kategoros, could become an epithet of the Antichrist: Revelation 12:10, see Matthew 7:1-2). In Christ there are no categories and thus neither male nor female (Galatians 3:28).
Strikingly, the Hebrew word for female, namely נקבה (neqeba), derives from a word for hole or receipt, which demonstrates that in the Hebrew mind, a female was known as that which had to be entered and impregnated (which explains the dwelling of God's Spirit in the tabernacle; Israel's national feminine reproductive apparatus). The Greek word for female derives from the word for nipple, which demonstrates that to the Greek mind, the conception had already taken place and the nipples were getting ready to nourish the child. Canaan was Israel's proverbial "land of milk and honey", which doesn't so much speak of nutritious natural liquids but rather of levels of instruction and particularly instruction of young children (see our articles on Malta, meaning honey, and Deborah, meaning bee).
Our Greek noun θελυς (thelus), meaning female, is used 5 times; see full concordance.